MRCOOL
DIY 5th Gen 12,000 BTU (DIY-12-HP-WM-115D25-O)
The MRCOOL DIY 5th Gen 12K is a single-zone ductless heat pump rated 23.5 SEER2 / 12.5 EER2 / 10.2 HSPF2 on low-GWP R-454B. MRCOOL sells it as a do-it-yourself kit with a pre-charged QuickConnect line set that needs no vacuum pump, but under EPA Section 608 connecting the refrigerant lines is certified-technician work.
$1,880
Live price at SylvanePrice checked Oct 8, 2026
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Will it cool your room?
This has more cooling than your 150 sq ft room needs. It can short-cycle and leave the air cool but humid.
Mini-splits are rated on SEER2, a seasonal scale, not the ENERGY STAR annual-kWh figure this dollar estimate is built from, so there is no comparable figure to show here. A blank is missing data, not a worse result: a mini-split is often the more efficient choice.
At a glance
Best for whole-room heating and cooling up to about 550 sq ft.
Performance
- Cooling capacity
- 12,000 BTU · 3.5 kW
- Heating capacity
- Yes
- Heats down to
- -13°F outdoors
- Room coverage
- up to 550 sq ft
- Energy Star
- Yes
- SEER2
- 23.5
- EER2
- 12.5
- Annual energy (cooling)
- Not published
Noise, size & features
- Model number
- DIY-12-HP-WM-115D25-O
- Indoor noise
- 43 dB(A)about as loud as a quiet library
- Outdoor noise
- Not published
- Indoor unit
- 31.57 x 11.69 x 7.44 in
- Outdoor unit
- 30.1 x 21.8 x 11.9 in (W x H x D)
- Refrigerant
- R-454B
- Wi-Fi / app
- Yes
- Outdoor unit needed
- Yes
- Power supply
- 115 V
- Warranty
- Eligible for MRCOOL Care Program; 7-Year Compressor Warranty; 5-Year Limited Parts Warranty
SEER2, EER2, heating limit, supply voltage, refrigerant, outdoor unit size and warranty are from Sylvane's published specifications for this exact configuration, checked Oct 2, 2026.
What is good
- Pre-charged, no-vacuum QuickConnect line set, so there is no refrigerant charging on site
- High 23.5 SEER2 with low-GWP R-454B refrigerant
- ENERGY STAR Most Efficient and runs on a standard 115V circuit
What to watch
- Costs much more than a window or portable unit for a single zone
- Requires drilling a 3 inch wall penetration and mounting an outdoor condenser
- WiFi needs a separate add-on module, not built in
Installation & the rules that apply
This is a single split. This is where regulation bites. Under EPA Section 608 the refrigerant circuit may only be opened by a certified technician, and the EPA is explicit that this includes connecting or disconnecting the pre-charged line sets sold with "DIY" mini-split kits. No federal law stops you doing the mounting, bracketing and line routing yourself, but handling the refrigerant without certification voids the warranty and is a violation. Most US jurisdictions also require permits for a new outdoor unit: typically mechanical or building for the wall penetration and mount, plus electrical for the dedicated 240 V circuit and disconnect. An HOA nearly always has to approve exterior equipment in advance, and local noise ordinances can cap how loud the condenser may be at the property line. This varies by city and county, so confirm with your building department before buying hardware.
DIY kit, certified refrigerant hookup
R-454B
Common questions about the MRCOOL DIY 5th Gen 12,000 BTU (DIY-12-HP-WM-115D25-O)
- How loud is the MRCOOL DIY 5th Gen 12,000 BTU (DIY-12-HP-WM-115D25-O)?
- 43 dB(A) indoors, about as loud as a quiet library.
- How energy-efficient is the MRCOOL DIY 5th Gen 12,000 BTU (DIY-12-HP-WM-115D25-O)?
- Its efficiency rating is SEER2 23.5, and it is ENERGY STAR certified.
- What size room does the MRCOOL DIY 5th Gen 12,000 BTU (DIY-12-HP-WM-115D25-O) cool?
- It is rated to cool a room up to 550 sq ft (12,000 BTU · 3.5 kW).
- Do I need a professional to install the MRCOOL DIY 5th Gen 12,000 BTU (DIY-12-HP-WM-115D25-O)?
- Partly. MRCOOL sells it as a do-it-yourself kit: the line set comes pre-charged with quick-connect fittings, so there is no vacuum pump or refrigerant charging on site, and you can mount the units and route the lines yourself. But under EPA Section 608 connecting refrigerant lines is certified-technician work, so plan on a certified technician for that connection. Usually needs permission.
- Does the MRCOOL DIY 5th Gen 12,000 BTU (DIY-12-HP-WM-115D25-O) heat as well as cool?
- Yes. It also heats.
- How cold can it get outside before the MRCOOL DIY 5th Gen 12,000 BTU (DIY-12-HP-WM-115D25-O) stops heating?
- Its retailer's specification for this exact configuration rates it to keep heating down to -13°F outdoors. That is its operating limit, not its full output: a heat pump delivers less heat as it gets colder, so size it for your coldest days.
How MRCOOL compares with other brands
Both lineups at every size both brands sell in stock, with live prices, ratings and the warranty each listing states.
How the MRCOOL DIY line compares
Both lines at every size both sell in stock, with live prices, ratings, recalls and what each maker says about its line.
Is a split even the right type?
Compare splits against the other types on price, noise, efficiency and install.
Buying guides for a single split like this
The questions buyers ask, answered from live prices and real specs. See where a single split like this fits.
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